Users are increasingly performing tasks using remote computing resources, which may be offered through a shared-resource environment. This has many advantages, as users do not have to purchase and maintain dedicated hardware and software, and instead can pay for only those resources that are utilized at any given time, where those resources typically will be managed by a resource provider. Users can perform tasks such as storing data or executing applications using various types of resources offered by the resource provider. It can be difficult, however, to ensure that all the resources are properly configured in such an environment, particularly as the usage evolves over time. As an example, there may be port settings on a firewall that end up being different from the port settings on a corresponding host machine allocated to a customer as part of a resource allocation. While some of these differences may be intentional, the differences can also be indicative of a potential misconfiguration. Since it is difficult to determine which ports should be open on the host machine, or a customer may not want to share that information, it can be difficult to identify potential misconfigurations.